I’m surprised to see links to university extension advice posted before guiding you to our forum guides section. There is information there I consider much more useful than what you will get written by some advisor that has no experience managing fruit trees in a home orchard setting and usually gets their info from information compiled for commercial growers who must have pristine fruit that is grown under heavy pest pressure due to the extent of commercial production. Once a pest finds one tree in an orchard useful to it, it tends to spread throughout the orchard.
Your pictures showed some pretty bad cedar apple rust- bad cases can cause complete early defoliation of apple leaves which can in itself destroy the crop. It is certainly reducing your annual growth already.